To date, there has been known an electric power steering driving unit that is provided with an electric motor that outputs auxiliary torque to the handwheel of a vehicle and a control apparatus that performs driving control of the electric motor and in which the control apparatus is mounted in the electric motor. In general, as the method of driving the electric motor, a PWM method is utilized; the PWM method is realized by pulse-driving the electric motor by use of a semiconductor switching device. In the case where a large current is controlled by the semiconductor switching device, a great deal of EMI noise occurs, as an adverse effect thereof. Accordingly, in order to prevent the noise from being emitted to the outside of the apparatus, a noise filter is incorporated in the control apparatus (e.g., refer to Patent Document 1).
As far as the motor driving apparatus disclosed in Patent Document 1 is concerned, there has been proposed a motor driving apparatus in which an integrated power module is formed of a plurality of switching devices so that it can be utilized for various kinds of motors such as a brush motor and a three-phase brushless motor.
The motor driving apparatus disclosed in Patent Document 1 has a structure in which a plurality of switching devices for controlling the electric power of an electric motor are integrated into a module and this power module is mounted on a heat sink and in which a control board 33 on which small-current devices such as a microcomputer and the like are mounted is incorporated and a control unit drives the power module. The motor drive apparatus incorporates a choke coil inside the heat sink on which the power module is mounted, so that an EMI noise filter for preventing the EMI noise from leaking out of the power supply line is configured. Patent Document 1 does not describe the detail of the configuration of the filter; however, it is conceivable that a normal mode filter or a common mode filter is anticipated.